In response to the increasing seriousness of global environmental issues, energy issues, and the like, a solar cell is attracting attention as clean energy-generating means with no concern over depletion. In a case in which a solar cell is used outdoors such as on the roof of a building, it is usual to use the solar cell in a solar cell module form.
Generally, the solar cell module is manufactured in the following order. First, a crystalline solar cell element (hereinafter also referred to as a power generation element or a cell) formed of polycrystalline silicon or monocrystalline silicon, or a thin film-type solar cell element obtained by forming an extremely thin (several micrometers) film of amorphous silicon or crystal silicon on a glass substrate or the like is manufactured.
Next, to obtain a crystalline solar cell module, a protective sheet (a transparent surface protective member) for the solar cell module, an encapsulating material for solar cell, the crystalline solar cell element, an encapsulating material for solar cell, and a protective sheet (a back surface protective member) for the solar cell module are sequentially laminated.
Meanwhile, to obtain a thin film-based solar cell module, a thin film-type solar cell element, an encapsulating material for solar cell, and a protective sheet (a back surface protective member) for the solar cell module are sequentially laminated. After that, the solar cell module is manufactured using a lamination method or the like in which the above-described laminate is suctioned in a vacuum, heated and pressed. The solar cell module manufactured in the above-described manner is weather resistant and is also suitable for outdoor use such as on the roof of a building.
An ethylene/vinyl acetate copolymer (EVA) film is widely used as an encapsulating material for solar cell due to its excellent transparency, flexibility, adhesiveness, and the like. However, in a case in which an EVA composition was used as a constituent material for an encapsulating material for solar cell, there was a concern over the possibility of a component being generated by the decomposition of EVA such as acetic acid gas affecting a solar cell element.
In contrast to the ethylene/vinyl acetate copolymer film, a resin composition for an encapsulating material for solar cell has been proposed which is composed of an ethylene/α-olefin copolymer, an organic peroxide, and a phenol-based antioxidant (for example, refer to Patent Document 1). The resin composition for an encapsulating material for solar cell has favorable productivity, does not corrode metal, and is excellent in terms of heat resistance, light transmittance, transparency, and adhesiveness to a substrate of a transparent surface protective member.
In addition, a resin composition for an encapsulating material for solar cell has been proposed which is composed of an ethylene/α-olefin copolymer, and an antioxidant having a phosphite ester structure and a phenol structure in the same molecule (for example, refer to Patent Document 2). The resin composition for an encapsulating material for solar cell is excellent in terms of heat stability, oxidization stability, and hue stability during a molding process and is improved in terms of the generation and attachment of gum at the nozzle outlet of an extruder.